Separator, and preparation method therefor and use thereof

Abstract

Provided in the present application are a separator, and a preparation method therefor and the use thereof. The separator comprises a base membrane and a coating layer arranged on the surface of at least one side of the base membrane, wherein the coating layer comprises a three-dimensional skeleton formed by a layered bimetal hydroxide, which overlaps each other, and polymer microspheres disorderly distributed in the three-dimensional skeleton. Under the combined action of the three-dimensional skeleton and the polymer microspheres, the present application can both improve the interface adhesion between the separator and an electrode sheet, and enable the separator to have good air permeability and excellent electrolyte wettability and can improve the battery capacity and cycle stability.

Description

A diaphragm, its preparation method and application Technical Field

[0001] This application relates to the field of battery technology, such as a separator, its preparation method, and its application. Background Technology

[0002] Global demand for separators continues to grow, and the market is enormous. Currently, to further improve the interfacial adhesion between the separator and the electrode and reduce the decay of the cell's cycle capacity, power battery separators and energy storage battery separators are usually coated with organic materials to give them better electrode adhesion performance. However, the addition of polymer coatings will reduce the permeability.

[0003] Therefore, there is an urgent need to provide a diaphragm that can combine air permeability with interfacial adhesion to the electrode. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0005] This application provides a separator, its preparation method, and its application. In the separator of this application, the coating layer comprises a three-dimensional framework formed by overlapping layered bimetallic hydroxides, and polymer microspheres randomly distributed within the three-dimensional framework. The combined effect of the three-dimensional framework and the polymer microspheres improves the interfacial adhesion between the separator and the electrode, and also gives the separator good air permeability and excellent electrolyte wettability, thereby contributing to improved battery capacity and cycle stability.

[0006] In a first aspect, this application provides a diaphragm, the diaphragm comprising a base membrane and a coating layer disposed on at least one surface of the base membrane;

[0007] The coating layer comprises a three-dimensional framework formed by overlapping layered bimetallic hydroxides, and polymer microspheres randomly distributed within the three-dimensional framework.

[0008] In one embodiment, the layered bimetallic hydroxide has a layered porous structure.

[0009] In this application, based on the three-dimensional skeleton formed by the overlapping of layered bimetallic hydroxides, the layered bimetallic hydroxides themselves also have a layered porous structure, which can further improve the air permeability of the membrane.

[0010] In one embodiment, the layered bimetallic hydroxide includes at least one of magnesium-aluminum bimetallic hydroxide, lithium-aluminum bimetallic hydroxide, zinc-aluminum bimetallic hydroxide, and nickel-aluminum bimetallic hydroxide, and may be selected as lithium-aluminum bimetallic hydroxide.

[0011] A layered bimetallic hydroxide (LDH) is represented as [M 2+ 1-x M 3+ x (OH)2] x+ A y- x / y ·nH2O, where M 2+ and M 3+ They are divalent and trivalent metal cations, respectively, A y- This represents interlayer cations, such as magnesium-aluminum bimetallic hydroxide, zinc-aluminum bimetallic hydroxide, or nickel-aluminum bimetallic hydroxide.

[0012] Besides M 2+ / M 3+ Besides the typical layered bimetallic hydroxides, there is another unique type of layered bimetallic hydroxide, namely lithium aluminum bimetallic hydroxide (LiAl-LDH), with the molecular formula [LiAl2(OH)6]. + A y- H₂O, because lithium ions are alkali metal cations that can intercalate into the LDH structure without damaging it. In the LiAl-LDH structure, the cation Li… + Located in the hollow octahedral position within the Al(OH)3 layer, where Al 3+ Occupying two-thirds of the octahedral positions, they contribute to the positive charge of the hydroxide layer, thus possessing a higher anion exchange capacity. Furthermore, lithium aluminum bimetallic hydroxide is a chemical substance that effectively guides lithium deposition. Its unique layered porous structure provides abundant lithium-ion diffusion pathways, exhibits good affinity for the electrolyte, and inhibits lithium dendrite formation.

[0013] In summary, this application can optionally use lithium aluminum bimetallic hydroxide combined with polymer microspheres, and the corresponding separator is suitable for use in lithium-ion batteries, which can improve the electrochemical performance of the battery. However, the use of separators with magnesium aluminum bimetallic hydroxide, zinc aluminum bimetallic hydroxide, or nickel aluminum bimetallic hydroxide in lithium-ion batteries may cause short circuits.

[0014] In one embodiment, the particle size D50 of the layered bimetallic hydroxide is 0.2 to 0.4 μm, for example, it can be any one or any two values ​​between 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm or 0.4 μm.

[0015] In one embodiment, the average pore size of the layered bimetallic hydroxide is 3.0 to 4.5 nm, for example, it can be any one or any two values ​​between 3.0 nm, 3.1 nm, 3.2 nm, 3.3 nm, 3.4 nm, 3.5 nm, 3.8 nm, 4 nm, 4.2 nm or 4.5 nm.

[0016] In one embodiment, the specific surface area of ​​the layered bimetallic hydroxide is 25–40 m². 2 / g, for example, could be 25m 2 / g、26m 2 / g、27m 2 / g、28m 2 / g、30m 2 / g、32m 2 / g、35m 2 / g、38m 2 / g or 40m 2 The range of values ​​between any one or any two values ​​in / g, etc.

[0017] In this application, when the specific surface area of ​​the layered bimetallic hydroxide is >40 m², 2 At a specific surface area of ​​<25 m² / g, the micropores on the surface of the layered bimetallic hydroxide particles are relatively few, which will have a certain impact on air permeability and affect lithium-ion transport in the later stage. Furthermore, the corresponding slurry viscosity is too high, leading to poor flowability. Coating on the machine requires cumbersome debugging and process adjustment. Reducing the viscosity by lowering the slurry solids content will affect the coating process efficiency, and low slurry solids content will lead to abnormalities such as missed coating and uneven coating, thus affecting the membrane performance. 2 The porous structure and the three-dimensional network formed by its own overlapping components result in excessively high porosity in the membrane, leading to poor thermal stability and mechanical properties. Therefore, the specific surface area of ​​layered bimetallic hydroxides is 25–40 m² / g. 2 / g is most suitable.

[0018] In this application, the specific surface area of ​​the layered bimetallic hydroxide is closely related to the pore size, particle size, viscosity of the coating slurry, and the corresponding membrane porosity, air permeability, and thermal stability.

[0019] In one embodiment, the polymer microspheres comprise polyethylene wax microspheres and / or polyvinylidene fluoride (PVDF) microspheres.

[0020] In one embodiment, the polyethylene wax microspheres have a core-shell structure, with the core material comprising hydroxylated polyethylene and the shell material comprising polyacrylate.

[0021] In this application, the polyethylene wax microspheres have a core-shell structure, with the polyacrylate outer shell providing high adhesion and the hydroxylated polyethylene core providing chemical stability. In addition to excellent electrode adhesion performance, the polyethylene wax microspheres have a low swelling rate and are fluorine-free, meeting both environmental protection and adhesion performance requirements.

[0022] In one embodiment, the particle size D50 of the polyethylene wax microspheres is 0.8 to 1.2 μm, for example, it can be any one or any two values ​​between 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.05 μm, 1.1 μm, 1.15 μm or 1.2 μm.

[0023] In this application, the particle size D50 of polyethylene wax microspheres is larger than that of layered bimetallic hydroxide, which results in more contact points between the polyethylene wax microspheres and the electrode, greatly improving the hot-pressing bonding performance of the diaphragm electrode.

[0024] When the particle size D50 of polyethylene wax microspheres is less than 0.8 μm, the smaller particle size makes them prone to clogging, leading to a decrease in the porosity of the coating layer and affecting the air permeability of the diaphragm. Simultaneously, the prepared slurry is prone to agglomeration, and with increasing storage time, it undergoes both soft and hard sedimentation, resulting in a rapid increase in viscosity and loss of fluidity, making it unsuitable for use in the machine. Diluting it with water to a usable state will affect process efficiency, and the coated film is prone to uneven coating, missed coating, and other surface defects. Conversely, when the D50 of polyethylene wax microspheres is greater than 1.2 μm, the increased D50 size results in a smaller contact surface area, leading to insufficient adhesion to the electrode after hot pressing.

[0025] In one embodiment, the ratio of the particle size D50 of the polyethylene wax microspheres to the particle size D50 of the layered bimetallic hydroxide is 2 to 6, for example, it can be any one or any two values ​​between 2, 3, 4, 5 or 6.

[0026] In one embodiment, the particle size D50 of the polyvinylidene fluoride microspheres is 0.2 to 0.5 μm, for example, it can be any one or any two values ​​between 0.2 μm, 0.25 μm, 0.3 μm, 0.4 μm or 0.5 μm.

[0027] In one embodiment, the mass ratio of the polymer microspheres to the layered bimetallic hydroxide is (1 to 1.5):1, for example, it can be any one or any two values ​​between 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1.

[0028] In one embodiment, a plurality of polymer microspheres are randomly distributed in the three-dimensional skeleton, at least some of which protrude from the surface of the three-dimensional skeleton, with a height of 0.2 to 0.4 nm.

[0029] In this application, "multiple" refers to at least two, such as any one or any range of two values, including 2, 5, 10, 20, 50, 100, 200, or 500. "At least some polymer microspheres protrude from the surface of the three-dimensional framework" includes two cases: some polymer microspheres protrude from the surface of the three-dimensional framework, or all polymer microspheres protrude from the surface of the three-dimensional framework.

[0030] In one embodiment, the coating layer further includes a binder and a dispersant.

[0031] In one embodiment, the adhesive comprises any one or a combination of at least two of acrylic acid, polyacrylate, or polyurethane.

[0032] In one embodiment, the dispersant includes anionic surfactants and / or polymeric dispersants.

[0033] Optionally, the anionic surfactant includes sulfate esters and / or alkylphenol polyoxyethylene ethers.

[0034] Optionally, the polymer dispersant includes polyethylene glycol and / or polyvinyl ester.

[0035] In one embodiment, the height of the coating layer is 1 to 1.2 μm, for example, it can be any one or any two values ​​between 1 μm, 1.05 μm, 1.1 μm, 1.15 μm or 1.2 μm.

[0036] In one embodiment, the bulk density of the coating layer is 1.2–1.5 g / cm³. 3 For example, it could be 1.1 g / cm³ 3 1.15g / cm 3 1.2g / cm 3 1.25g / cm 3 1.3g / cm 3 1.35g / cm 3 1.4g / cm 3 Or 1.5g / cm 3 The range of values ​​between any one or any two values ​​in the range.

[0037] In one embodiment, the porosity of the membrane is 40-55%, for example, it can be any one or any two values ​​between 40%, 41%, 42%, 43%, 44%, 45%, 47%, 48%, 50%, 52% or 55%.

[0038] Secondly, this application provides a method for preparing the diaphragm described in the first aspect, the method comprising:

[0039] (1) A slurry is obtained by mixing layered bimetallic hydroxide, a dispersion containing polymer microspheres and a solvent;

[0040] (2) The slurry is coated onto at least one side surface of the base film to obtain the diaphragm.

[0041] In one embodiment, the layered bimetallic hydroxide includes at least one of magnesium-aluminum bimetallic hydroxide, lithium-aluminum bimetallic hydroxide, zinc-aluminum bimetallic hydroxide, and nickel-aluminum bimetallic hydroxide, and may be selected as lithium-aluminum bimetallic hydroxide.

[0042] In one embodiment, the solvent in step (1) includes water.

[0043] In one embodiment, the method for preparing the lithium-aluminum bimetallic hydroxide includes: mixing metallic Al and Li-containing compounds... + and OH - The solutions were mixed and subjected to a hydrothermal reaction to obtain lithium aluminum bimetallic hydroxide.

[0044] The traditional Bayer process involves placing aluminum hydroxide / boehmite in a high-concentration sodium hydroxide solution at 270°C, resulting in Bayer solution. The generated tetrahedral aluminate ions, Al(OH)₄, form the solution. - Lithium ions are intercalated to form LiAl-LDH. The traditional Bayer process for preparing lithium aluminum bilayer hydroxides requires harsh conditions, resulting in significant energy waste and a slow reaction rate, making mass production difficult. The specific reaction process is shown below:

[0045] This application uses metallic Al and Li-containing compounds. + and OH - The preparation reaction process using the solution as raw material is shown below:

[0046] As can be seen from the above reaction equations, this application utilizes metallic Al and Li-containing compounds. + and OH - The solution reaction directly produces lithium aluminum bimetallic hydroxide.

[0047] This application uses metallic Al and compounds containing Li+ and OH-. -Using a solution as raw material, porous layered lithium aluminum bimetallic hydroxide particles are prepared. Compared with the traditional Bayer process, this method has two advantages: ① First, the reaction process is spontaneous and fast, and does not require a specific high temperature, which can save energy and is efficient and simple; ② The reaction process is exothermic, producing hydrogen gas. The heat and hydrogen generated by the reaction can be converted into electrical energy, which can save energy and recover energy, forming a resource recycling system.

[0048] In one embodiment, the particle size D50 of the metal Al is 0.1 to 0.3 μm, for example, it can be any one or any two values ​​between 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm or 0.3 μm.

[0049] In this application, controlling the particle size of metallic Al within a suitable range helps to form LiAl-LDH with appropriate particle size and specific surface area.

[0050] In one embodiment, the metal Al is obtained by mechanically ball milling aluminum foil.

[0051] In one embodiment, the temperature of the mechanical ball mill is controlled between 0 and 15°C. If the temperature exceeds 15°C, oxidation reaction is likely to occur on the surface of the aluminum foil.

[0052] In one embodiment, the Li-containing + and OH - The solution includes a LiOH solution with a concentration of 1 to 5 mol / L, for example, it can be any one or any two values ​​between 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0053] In this application, when the concentration of LiOH solution is less than 1 mol / L, the solution concentration is insufficient to advance the reaction.

[0054] In one embodiment, the preparation process of the LiOH solution includes: dissolving 2.4 to 12 kg of LiOH in 100 kg of water at 90 to 100°C to obtain the LiOH solution.

[0055] In one embodiment, the Al element in the metallic Al and the Li-containing element + and OH - The molar ratio of Li in the solution is 0.1 to 2, for example, it can be any one or any two values ​​between 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8 or 2.

[0056] In this application, when the Al / Li molar ratio is 0.1 ≤ Al / Li ≤ 2, the product mainly consists of a large amount of LiAl-LDH and a small amount of aluminum oxide byproducts, resulting in high-purity LiAl-LDH. As the Al / Li molar ratio increases, the amount of aluminum oxide increases, and the LiAl-LDH yield decreases.

[0057] When the molar ratio of Al to Li is greater than 2, i.e., the Al / Li molar ratio is >2, most of the products are mainly gibbsite and boehmite byproducts. The yield of LiAl-LDH products is too low. When used for coating lithium battery separators, the improvement in separator thickness and air permeability is not significant and does not meet the application requirements.

[0058] When the Al / Li molar ratio is less than 0.1, only an aluminate solution is formed, and lithium-aluminum bimetallic hydroxide is not formed. The coated separator prepared later cannot meet the air permeability requirements, therefore the slurry prepared from its product cannot be used for lithium-ion battery separator coating.

[0059] In one embodiment, the temperature of the hydrothermal reaction is 50–70°C, for example, it can be any one or any two values ​​between 50°C, 55°C, 60°C, 65°C or 70°C, and the time of the hydrothermal reaction is 20–24 h, for example, it can be any one or any two values ​​between 20 h, 21 h, 22 h, 23 h or 24 h.

[0060] In one embodiment, the mass fraction of the layered bimetallic hydroxide is 4 to 6% based on 100% of the mass of the slurry, for example, it can be any one or any two values ​​between 4%, 4.5%, 5%, 5.5% or 6%.

[0061] In this application, when the mass fraction of the layered bimetallic hydroxide is too high, the slurry viscosity will be too high, making coating difficult; when the mass fraction of the layered bimetallic hydroxide is too low, the thermal stability and mechanical properties of the diaphragm are limited, and the air permeability deteriorates.

[0062] In one embodiment, the solid content of the dispersion containing polymer microspheres is 28-32%, for example, it can be any one or any two values ​​between 28%, 29%, 30%, 31% or 32%.

[0063] In this application, when the solid content of the dispersion containing polymer microspheres is too high, the dispersion has poor fluidity and is not easily mixed evenly with the layered bimetallic hydroxide during the pulping process, making it prone to agglomeration and stratification. When the solid content of the dispersion containing polymer microspheres is too low, the polymer microspheres are prone to sedimentation, and after long storage time, they are prone to forming hard precipitates.

[0064] In one embodiment, the mass fraction of the polymer microspheres is 4 to 6% based on 100% of the slurry, for example, it can be any one or any two values ​​between 4%, 4.5%, 5%, 5.5% or 6%.

[0065] In this application, when the mass fraction of polymer microspheres is greater than 6%, the slurry system will have excessive viscosity and poor fluidity, requiring multiple adjustments during the coating process. At the same time, the excessive viscosity may lead to uneven distribution on the membrane surface. When the mass fraction of polymer microspheres is less than 4%, the adhesion performance of the prepared diaphragm to the electrode is limited.

[0066] In one embodiment, a binder and a dispersant are also added during the mixing process described in step (1).

[0067] In one embodiment, the mass fraction of the binder is 5 to 7% based on 100% of the mass of the slurry, for example, it can be any one or any two values ​​between 5%, 5.5%, 6%, 6.5% or 7%.

[0068] In one embodiment, the mass fraction of the dispersant is 0.1% to 0.5% based on 100% of the mass of the slurry, for example, it can be any one or any two values ​​between 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%.

[0069] In one embodiment, the solid content of the slurry is 13-19%, for example, it can be any one or any two values ​​between 13%, 14%, 15%, 16%, 17%, 18% or 19%.

[0070] As an optional technical solution of this application, the preparation method specifically includes the following steps:

[0071] (I) Add metallic Al with a particle size D50 of 0.1–0.3 μm to a Li-containing substrate. + and OH - The solution was then subjected to a hydrothermal reaction at 50–70°C for 20–24 h. After solid-liquid separation and washing, the solution was dried at 60–70°C for 5–8 h to obtain lithium aluminum bimetallic hydroxide.

[0072] Among them, the Li-containing + and OH - The solution is a LiOH solution with a concentration of 1–5 mol / L; the molar ratio of Al in the metallic Al to Li in the LiOH solution is 0.1–2; the lithium-aluminum bimetallic hydroxide has a layered porous structure with a specific surface area of ​​25–40 m² / L. 2 / g, with an average pore size of 3.0–4.5 nm and a particle size D50 of 0.2–0.4 μm;

[0073] (II) The lithium aluminum bimetallic hydroxide, the dispersion containing polymer microspheres, and the solvent are mixed at a speed of 1800-2000 rpm for 2-3 hours. Then, a binder is added to the resulting mixture, and the mixture is mixed at a speed of 1000-1200 rpm for 1-2 hours. After that, a dispersant is added, and the mixture is mixed at a speed of 500-800 rpm for 0.5-2 hours to obtain a slurry. The solid content of the slurry is 13-19%.

[0074] The polymer microspheres include polyethylene wax microspheres, which have a core-shell structure. The core material includes hydroxyl polyethylene, and the shell material includes polyacrylate. The particle size D50 of the polyethylene wax microspheres is 0.8–1.2 μm. The solid content of the dispersion containing the polymer microspheres is 28–32%. The mass ratio of the polymer microspheres to the lithium aluminum bimetallic hydroxide is (1–1.5):1. The binder includes any one or a combination of at least two of acrylic acid, polyacrylate, or polyurethane. The dispersant includes anionic surfactants and / or polymeric dispersants.

[0075] (III) The slurry is coated onto at least one side surface of the base film using a micro-concave roller coating method, and then dried at 60-70°C to obtain the diaphragm.

[0076] In one embodiment, the solid-liquid separation method in step (I) includes filtration, wherein the mesh size of the filter is 2000 to 3000 mesh.

[0077] Thirdly, this application provides a battery comprising the separator described in the first aspect or a separator prepared using the preparation method described in the second aspect.

[0078] The battery includes, but is not limited to, a lithium-ion battery.

[0079] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0080] Compared with related technologies, the beneficial effects of this application are as follows:

[0081] This application provides a separator in which the three-dimensional skeleton formed by the overlapping of layered bimetallic hydroxides has a large porosity. Under the combined action of the three-dimensional skeleton and polymer microspheres, it can not only improve the interfacial adhesion between the separator and the electrode, but also give the separator good air permeability and excellent electrolyte wettability, thereby improving battery capacity and cycle stability.

[0082] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0083] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0084] Figure 1 is a schematic diagram of the structure of the diaphragm prepared in Example 1 of this application.

[0085] Figure 2 is a SEM image of the diaphragm prepared in Example 1 of this application.

[0086] Figure 3 is a SEM image of LiAl-LDH in Embodiment 1 of this application.

[0087] Figure 4 is a schematic diagram of the structure of polyethylene wax microspheres in Example 1 of this application.

[0088] Figure 5 is the infrared spectrum of the polyethylene wax microspheres in Example 1 of this application.

[0089] Figure 6 is a schematic diagram of the diaphragm and electrode sheet before and after hot pressing according to the embodiments of this application.

[0090] Among them, 1-base membrane; 2-three-dimensional framework; 3-polymer microspheres; 4-active material; 5-current collector. Detailed Implementation

[0091] The technical solution of this application will be further described below through specific implementation methods.

[0092] Example 1

[0093] This embodiment provides a diaphragm, as shown in FIG1. ​​The diaphragm includes a base film 1 and a coating layer disposed on both sides of the base film 1, wherein the thickness of the coating layer on one side is 1μm.

[0094] The base film 1 is a 7μm thick PE film, grade SW807C, purchased from Shenzhen Xingyuan Material Technology Co., Ltd.; the coating layer includes a three-dimensional framework 2 formed by overlapping lithium aluminum bimetallic hydroxide (LiAl-LDH), and multiple polymer microspheres 3 randomly distributed in the three-dimensional framework 2, some of which protrude from the surface of the three-dimensional framework 2, with a height of 0.2-0.4nm; LiAl-LDH has a layered porous structure with a specific surface area of ​​25m². 2 / g, with an average pore size of 4.5nm and a particle size D50 of 0.4μm; the polymer microspheres 3 are specifically polyethylene wax microspheres with a core-shell structure, the core material being hydroxyl polyethylene and the outer shell material being polyacrylate; the particle size D50 of the polyethylene wax microspheres is 0.8μm, and the ratio of the particle size D50 of the polyethylene wax microspheres to that of LiAl-LDH is 2.0; the ratio of the total mass of the polyethylene wax microspheres to the mass of LiAl-LDH is 1:1; the binder is acrylic acid, and the dispersant is polysulfate.

[0095] This embodiment provides a method for preparing the above-mentioned diaphragm, the method comprising:

[0096] (1) Dissolve 7.2 kg of LiOH in 100 kg of deionized water at 90 °C to prepare a 3 mol / L LiOH solution; add metallic Al powder with a particle size D50 of 0.3 μm to the LiOH solution, with an Al / Li element molar ratio of 1.0. The reaction will generate a large amount of heat and hydrogen gas, and the reaction time is 24 h. Filter the obtained solid through a 3000 mesh filter, wash the surface salt with deionized water, and dry the solid product in an oven at 70 °C for 8 h to obtain LiAl-LDH.

[0097] (2) LiAl-LDH, a dispersion containing polyethylene wax microspheres, and water were mixed at 1200 rpm for 1 h. The polyethylene wax microspheres had a core-shell structure, with the core material being hydroxyl polyethylene and the shell material being polyacrylate. The particle size D50 of the polyethylene wax microspheres was 0.8 μm. The solid content of the dispersion containing polyethylene wax microspheres was 30%, and the solvent in the dispersion was water. The mass ratio of polyethylene wax microspheres to LiAl-LDH was 1:1. Then, the mixture was added to the obtained... 6% acrylic acid (based on 100% of the slurry mass) was added to the mixed product and mixed at 1000 rpm for 1 hour. Then, 0.1% polysulfate dispersant (based on 100% of the slurry mass) was added to the resulting mixed product and mixed at 600 rpm for 0.5 hours to obtain the slurry. Based on 100% of the slurry mass, the mass fraction of LiAl-LDH in the slurry was 4.0%, the mass fraction of polyethylene wax microspheres was 5.0%, and the total solids content of the slurry was 15%.

[0098] (3) The slurry is coated onto both sides of the base film 1 using a micro-concave roller coating method and dried at 65°C to obtain the diaphragm.

[0099] Figure 2 shows the SEM image of the diaphragm prepared in this embodiment. The SEM image shows that the layered LiAl-LDH structure overlaps to form a three-dimensional network structure, thus providing a certain porosity. The spherical polyethylene wax microspheres are randomly arranged within the overlapping three-dimensional network framework of LiAl-LDH, with most of the polyethylene wax microspheres protruding from the surface of the three-dimensional framework, and a small portion being embedded. This reduces the porosity to some extent, but the impact is not significant. Because the polyethylene wax microspheres are larger than LiAl-LDH, they have more contact points with the electrode, thus greatly improving the hot-pressing adhesion performance of the electrode.

[0100] Figure 3 shows the SEM image of LiAl-LDH in this embodiment. As can be seen from the figure, the LiAl-LDH wafer presents as sheet-like polygons, which can be interconnected to form a three-dimensional mesh structure.

[0101] Figure 4 shows a schematic diagram of the polyethylene wax microspheres in this embodiment. As can be seen from the figure, the polyethylene wax microspheres consist of an outer shell and an inner shell. The outer shell is a polyacrylate shell, and the inner shell is a hydroxyl polyethylene core. The outer shell provides high adhesion, while the inner shell provides chemical stability.

[0102] Figure 5 shows the infrared spectrum of the polyethylene wax microspheres in this embodiment. As can be seen from the figure, at 3500 cm⁻¹... -1 A peak representing the stretching vibration of the hydroxyl group (-OH) appeared nearby, at 2420 cm⁻¹. -1 A peak representing the methylene-CH2 stretching vibration appeared nearby, at 1680 cm⁻¹. -1 Nearby, a peak representing the carbonyl-C=O stretching vibration appeared, which corresponds exactly to the functional group in the polyethylene wax microsphere structure diagram in Figure 4.

[0103] Example 2

[0104] The difference between this embodiment and Embodiment 1 is that the particle size D50 of the polyethylene wax microspheres is 1.2 μm, and the ratio of the particle size D50 of the polyethylene wax microspheres to that of LiAl-LDH is 3.0.

[0105] The remaining parameters are the same as in Example 1.

[0106] Example 3

[0107] The difference between this embodiment and Embodiment 1 is that the LiAl-LDH has a particle size D50 of 0.3 μm, an average pore size of 3.75 nm, and a specific surface area of ​​2 m². 2 / g, the ratio of the particle size D50 of polyethylene wax microspheres to LiAl-LDH is 2.67.

[0108] The remaining parameters are the same as in Example 1.

[0109] Example 4

[0110] The difference between this embodiment and Embodiment 1 is that the LiAl-LDH has a particle size D50 of 0.3 μm, an average pore size of 3.75 nm, and a specific surface area of ​​32 m². 2 / g, the particle size D50 of polyethylene wax microspheres is 1.2μm, and the ratio of the particle size D50 of polyethylene wax microspheres to that of LiAl-LDH is 4.0.

[0111] The remaining parameters are the same as in Example 1.

[0112] Example 5

[0113] The difference between this embodiment and Embodiment 1 is that the LiAl-LDH has a particle size D50 of 0.2 μm, an average pore size of 3.0 nm, and a specific surface area of ​​40 m². 2 / g, the ratio of the particle size D50 of polyethylene wax microspheres to LiAl-LDH is 4.0.

[0114] The remaining parameters are the same as in Example 1.

[0115] Example 6

[0116] The difference between this embodiment and Embodiment 1 is that the LiAl-LDH has a particle size D50 of 0.2 μm, an average pore size of 3.0 nm, and a specific surface area of ​​40 m². 2 / g, the particle size D50 of polyethylene wax microspheres is 1.2μm, and the ratio of the particle size D50 of polyethylene wax microspheres to that of LiAl-LDH is 6.0.

[0117] The remaining parameters are the same as in Example 1.

[0118] Example 7

[0119] The difference between this embodiment and Embodiment 1 is that the LiAl-LDH has a particle size D50 of 0.15 μm, an average pore size of 2.5 nm, and a specific surface area of ​​45 m². 2 / g, the ratio of the particle size D50 of polyethylene wax microspheres to LiAl-LDH is 5.33.

[0120] The remaining parameters are the same as in Example 1.

[0121] Example 8

[0122] The difference between this embodiment and Embodiment 1 is that the LiAl-LDH has a particle size D50 of 0.1 μm, an average pore size of 2.6 nm, and a specific surface area of ​​45 m². 2 / g, the ratio of the particle size D50 of polyethylene wax microspheres to LiAl-LDH is 8.0.

[0123] The remaining parameters are the same as in Example 1.

[0124] Example 9

[0125] The difference between this embodiment and Embodiment 6 is that the particle size D50 of the polyethylene wax microspheres is 1.3 μm, and the ratio of the particle size D50 of the polyethylene wax microspheres to that of LiAl-LDH is 6.5; some of the polyethylene wax microspheres in the diaphragm protrude from the surface of the three-dimensional skeleton, and the height of the protruding part is 0.35 to 0.5 nm.

[0126] The remaining parameters are the same as in Example 6.

[0127] Example 10

[0128] The difference between this embodiment and Example 1 is that the particle size D50 of the polyethylene wax microspheres is 0.7 μm, and the ratio of the particle size D50 of the polyethylene wax microspheres to that of LiAl-LDH is 1.75; a slurry is prepared. Some of the polyethylene wax microspheres in the diaphragm protrude from the surface of the three-dimensional skeleton, and the height of the protruding part is 0 to 0.27 nm and is not zero.

[0129] The remaining parameters are the same as in Example 1.

[0130] Example 11

[0131] The difference between this embodiment and Embodiment 1 is that the amount of Al powder added is adjusted so that the molar ratio of Al / Li is 0.5.

[0132] The remaining parameters are the same as in Example 1.

[0133] Example 12

[0134] The difference between this embodiment and Embodiment 1 is that the amount of Al powder added is adjusted so that the molar ratio of Al / Li is 0.1.

[0135] The remaining parameters are the same as in Example 1.

[0136] Example 13

[0137] The difference between this embodiment and Embodiment 1 is that the amount of Al powder added is adjusted so that the molar ratio of Al / Li is 2.

[0138] The remaining parameters are the same as in Example 1.

[0139] Example 14

[0140] The difference between this embodiment and Embodiment 1 is that the preparation method of the LiAl-LDH particles includes:

[0141] Alumina was placed in a sodium hydroxide solution at a reaction temperature of 275°C for 5 hours, with a solid alumina to sodium hydroxide molar ratio of 3:1 and a sodium hydroxide solution concentration greater than 98.0%. After multiple washing, filtration, and drying, NaAl(OH)4 particles were obtained. These NaAl(OH)4 particles were then placed in a LiOH solution and reacted for 30 hours, generating a large amount of heat and hydrogen gas. After multiple washing, filtration, and drying, LiAl-LDH particles were obtained. All other parameters remained the same as in Example 1.

[0142] Example 15

[0143] The difference between this embodiment and Embodiment 1 is that, in step (2), the mass fraction of polyethylene wax microspheres in the slurry is adjusted to 2.0%. The remaining parameters are the same as in Embodiment 1.

[0144] Example 16

[0145] The difference between this embodiment and embodiment 1 is that in step (2), the mass fraction of LiAl-LDH in the slurry is adjusted to 6%, while the other parameters remain the same as in embodiment 1.

[0146] Example 17

[0147] The difference between this embodiment and embodiment 1 is that in step (2), the mass fraction of LiAl-LDH in the slurry is adjusted to 2%, while the other parameters remain the same as in embodiment 1.

[0148] Example 18

[0149] The difference between this embodiment and Embodiment 1 is that the polyethylene wax microspheres are replaced with PVDF microspheres with a particle size D50 of 0.35 μm.

[0150] The remaining parameters are the same as in Example 1.

[0151] Example 19

[0152] The difference between this embodiment and Embodiment 1 is that the mass ratio of polyethylene wax microspheres to LiAl-LDH is 1.5:1.

[0153] The remaining parameters are the same as in Example 1.

[0154] Example 20

[0155] The difference between this embodiment and Embodiment 1 is that the mass ratio of polyethylene wax microspheres to LiAl-LDH is 1.8:1.

[0156] The remaining parameters are the same as in Example 1.

[0157] Comparative Example 1

[0158] This comparative example provides a boehmite@polyethylene wax microsphere hybrid coating film. The difference between its preparation method and that of Example 1 is that step (1) in the preparation method is omitted, and LiAl-LDH in step (2) is replaced with boehmite (particle size D50 is 1 μm). The remaining parameters are the same as those of Example 1.

[0159] Comparative Example 2

[0160] This comparative example provides a pure LiAl-LDH coated separator. The preparation method differs from Example 1 in that the polyethylene wax microspheres in the slurry are omitted; the remaining steps and parameters are consistent with Example 1. The pure LiAl-LDH coated separator has a LiAl-LDH coating layer on both sides of the base membrane.

[0161] Performance testing

[0162] The following tests were performed on the diaphragms provided in the above embodiments and comparative examples:

[0163] (1) Breathability test:

[0164] ① Diaphragm porosity test according to GB / T36363-2018;

[0165] ② Test the air permeability of the diaphragm according to GB / T36363-2018.

[0166] (2) Coating density test:

[0167] Bulk density test was conducted according to GB / T-36363-2018;

[0168] (3) Heat shrinkage test:

[0169] Referring to GB / T12027-2004, the diaphragms were placed in a forced-air oven at 180℃ for 60 minutes for heat treatment to conduct a heat shrinkage test, and the thermal stability of the diaphragms was evaluated by the heat shrinkage test.

[0170] (4) Adhesion test:

[0171] Long strip-shaped separators were attached to the positive and negative electrode sheets respectively, and then placed on a hot press for hot pressing bonding. The positive electrode sheet was a lithium iron phosphate electrode sheet, and the negative electrode sheet was a graphite electrode sheet. The specific hot pressing parameters were: hot pressing temperature 90℃, hot pressing time 60s, and hot pressing pressure 6.5MPa. After hot pressing, the membrane was placed on a stretching machine for peel testing (speed 200mm / min), and the adhesion force values ​​between the separator and the positive electrode sheet and between the separator and the negative electrode sheet were recorded respectively.

[0172] Both the positive and negative electrodes include a current collector 5 and an active material 4 disposed on the surface of the current collector 5, as shown in Figure 6. Under hot-pressing conditions, the polymer microspheres 3 in the separator of this application will soften and deform, and the polymer microspheres 3 monomers will be riveted to the interface of the positive and negative electrodes. After hot pressing, the polymer microspheres 3 harden to become an intermediate connecting the base film 1 and the active material 4. The mechanical riveting effect of the polymer microspheres 3 and the electrode interface and the van der Waals force together give it good interfacial adhesion performance.

[0173] (5) Contact angle test:

[0174] The contact angle test is performed according to GB / T30447-2018. The wettability of the diaphragm is determined by the contact angle.

[0175] The test results are shown in Table 1. In the values ​​of positive and negative electrode adhesion, the left side represents the adhesion between the separator and the positive electrode, and the right side represents the adhesion between the separator and the negative electrode.

[0176] Table 1

[0177] analyze:

[0178] As shown in the embodiments, in the coating layer of the diaphragm provided in this application, LiAl-LDH overlaps to form a three-dimensional skeleton. This three-dimensional skeleton has a large porosity, resulting in good air permeability and a suitable coating layer packing density. Furthermore, the three-dimensional skeleton structure facilitates electrolyte absorption, giving the diaphragm a small contact angle, i.e., excellent electrolyte wettability. Simultaneously, the three-dimensional skeleton structure formed by LiAl-LDH provides the diaphragm with good thermal stability and low thermal shrinkage. In addition, because the LiAl-LDH overlaps to form a network structure with a certain degree of porosity, the relatively large and spherical polyethylene wax microspheres are embedded in the LiAl-LDH skeleton structure, thus having better contact sites. This indirectly compensates for the low adhesion between the positive and negative electrodes of the polyethylene wax microspheres with their small specific surface area, giving the diaphragm relatively good adhesion performance. In summary, the diaphragm provided in this application has excellent comprehensive performance.

[0179] From Example 1 to Example 6, as the particle size D50 of LiAl-LDH decreased (specific surface area increased), the air permeability showed an upward trend, within the range of 0.2 to 0.4 μm; however, as the particle size decreased and it was compounded with polyethylene wax microspheres, the bonding force between the positive and negative electrodes showed an upward trend. This may be due to the fact that the specific surface area of ​​LiAl-LDH gradually increased and formed a better bonding force with the polyethylene wax microspheres.

[0180] As can be seen from Examples 1 and 7, the particle size D50 of the lithium aluminum bimetallic hydroxide in Example 7 is too small, but it meets the particle size ratio range of polyethylene wax microspheres and LiAl-LDH. Compared with Example 1, the air permeability, thermal stability and adhesion performance of the membrane in Example 7 are worse.

[0181] As can be seen from Examples 1 and 8, the particle size D50 of the lithium aluminum bimetallic hydroxide in Example 8 is too small and the particle size ratio of polyethylene wax microspheres to LiAl-LDH is too large. Compared with Example 1, the air permeability, adhesion and electrolyte wettability of the diaphragm in Example 8 are worse.

[0182] As shown in Examples 1 and 9-10, when the particle size D50 of the polyethylene wax microspheres is too large, the particle size ratio between the polyethylene wax microspheres and the lithium aluminum bimetallic hydroxide is also too large, resulting in a larger protrusion height of the microspheres. This leads to a decrease in the gas permeability, adhesion, and electrolyte wettability of the diaphragm. The decreased adhesion is due to the smaller contact surface area of ​​the polyethylene wax microspheres as their size increases, resulting in a weaker bond strength after hot pressing with the electrode. Conversely, when the particle size D50 of the polyethylene wax microspheres is too small, the particle size ratio between the polyethylene wax microspheres and the lithium aluminum bimetallic hydroxide is also too small, resulting in a smaller protrusion height of the microspheres. This leads to a decrease in the gas permeability, adhesion, and electrolyte wettability of the diaphragm. Therefore, it was determined that a particle size D50 ratio of polyethylene wax microspheres to LiAl-LDH between 2 and 6 can meet the diaphragm performance requirements.

[0183] As shown in Examples 1 and 11-13, when 0.1 ≤ Al / Li ≤ 2, the product mainly consists of a small amount of aluminum oxide and a large amount of LiAl-LDH, resulting in high-purity LiAl-LDH and giving the membrane excellent thermal stability. With further increases in the concentration ratio, the amount of aluminum oxide produced also increases, leading to a decrease in yield, but improving the membrane's gas permeability and electrolyte wettability.

[0184] As can be seen from Examples 1 and 14, the LiAl-LDH particles prepared using the traditional Bayer process have an indistinct pore structure due to process differences, resulting in fewer pore structures formed after they overlap. Consequently, the air permeability, adhesion, and electrolyte wettability of the corresponding membrane are all reduced.

[0185] As can be seen from Examples 1 and 15, if the mass fraction of polyethylene wax microspheres in the slurry is too low during the preparation of the diaphragm, the air permeability and adhesion properties of the diaphragm will both decrease.

[0186] As can be seen from Examples 1 and 16-17, if the mass fraction of LiAl-LDH in the slurry is too low during the preparation of the diaphragm, the air permeability, thermal stability, adhesion and electrolyte wettability of the diaphragm will all deteriorate.

[0187] As shown in Example 18, in the coating layer of the diaphragm provided in this application, LiAl-LDH overlaps to form a three-dimensional skeleton, and PVDF microspheres are randomly distributed in the three-dimensional skeleton. This diaphragm exhibits good comprehensive properties such as air permeability, bulk density, thermal stability, adhesion, and electrolyte wettability. Comparing Example 1 and Example 18, it was found that the diaphragm using polyethylene wax microspheres has better comprehensive performance. In particular, the positive and negative electrode adhesion of the diaphragm using polyethylene wax microspheres is greater than that of the diaphragm using PVDF microspheres. This is mainly because the polyacrylate on the shell surface of the core-shell structure of the polyethylene wax microspheres gives the microspheres stronger adhesion. Under hot-pressing conditions, the polyethylene wax microspheres soften and deform, and the microsphere monomers are riveted to the positive and negative electrode interfaces. The mechanical riveting force and van der Waals force together give good interfacial adhesion.

[0188] As can be seen from Examples 1 and 19-20, when the mass ratio of polymer microspheres to lithium aluminum bimetallic hydroxide is too large, the gas permeability and electrolyte wettability of the diaphragm decrease; when the mass ratio of polymer microspheres to lithium aluminum bimetallic hydroxide is too large, the gas permeability, thermal stability and electrolyte wettability of the diaphragm decrease significantly.

[0189] As can be seen from the comparison between Example 1 and Comparative Example 1, the boehmite@polyethylene wax microsphere mixed coating diaphragm provided in Comparative Example 1 uses boehmite (AlOOH) as the ceramic material and is mixed with polyethylene wax microspheres for coating. Compared with the diaphragm provided in Example 1, the air permeability, thermal stability and electrolyte wettability of the diaphragm in Comparative Example 1 are all worse.

[0190] As can be seen from the comparison between Example 1 and Comparative Example 2, Comparative Example 2 is a pure LiAl-LDH coated diaphragm without the participation of polyethylene wax microspheres. Compared with the diaphragm provided in Example 1, the air permeability and adhesion performance of the diaphragm in this comparative example are reduced.

[0191] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A separator comprising a base film, and a coating layer disposed on at least one side surface of the base film; The coating layer comprises a three-dimensional framework formed by interlacing layered double hydroxides, and polymer microspheres randomly distributed in the three-dimensional framework.

2. The septum of claim 1, wherein, The layered double hydroxide has a layered porous structure.

3. The separator according to claim 1 or 2, wherein The layered double hydroxide comprises at least one of magnesium-aluminum double hydroxide, lithium-aluminum double hydroxide, zinc-aluminum double hydroxide and nickel-aluminum double hydroxide, and is optionally lithium-aluminum double hydroxide.

4. The separator according to any one of claims 1 to 3, wherein The particle size D50 of the layered double hydroxide is 0.2-0.4 μm.

5. The separator according to any one of claims 1 to 4, wherein The average pore size of the layered double hydroxide is 3.0-4.5 nm. Optionally, the specific surface area of the layered double hydroxide is 25-40 m 2 / g.

6. The separator according to any one of claims 1 to 5, wherein The polymer microspheres comprise polyethylene wax microspheres and / or polyvinylidene fluoride microspheres. Optionally, the polyethylene wax microspheres are of core-shell structure, the material of the inner core comprises hydroxyl polyethylene, and the material of the outer shell comprises polyacrylate. Optionally, the particle size D50 of the polyethylene wax microspheres is 0.8-1.2 μm. Optionally, the ratio of the particle size D50 of the polyethylene wax microspheres to the particle size D50 of the layered double hydroxide is 2-6. Optionally, the particle size D50 of the polyvinylidene fluoride microspheres is 0.2-0.5 μm.

7. The separator of any one of claims 1-6, wherein, The mass ratio of the polymer microspheres to the layered double hydroxide is (1-1.5) :

1. Optionally, a plurality of polymer microspheres are randomly distributed in the three-dimensional framework, and at least part of the polymer microspheres protrude from the surface of the three-dimensional framework, and the height of the protruding part is 0.2-0.4 nm.

8. The separator according to any one of claims 1 to 7, wherein The coating layer further comprises a binder and a dispersant. Optionally, the binder comprises any one or a combination of at least two of acrylic acid, polyacrylate or polyurethane. Optionally, the dispersant comprises an anionic surfactant and / or a polymer dispersant. Optionally, the thickness of the coating layer is 1-1.2 μm. Optionally, the coating layer has a bulk density of 1.2 to 1.5 g / cm3 3 ; Optionally, the porosity of the separator is 40-55%. 9.A method for preparing the separator of any one of claims 1-8, comprising: (1) mixing a layered double hydroxide, a dispersion liquid containing polymer microspheres and a solvent to obtain a slurry; (2) coating the slurry on at least one side surface of a base film to obtain the separator.

10. The production method according to claim 9, wherein The layered double hydroxide comprises at least one of magnesium-aluminum double hydroxide, lithium-aluminum double hydroxide, zinc-aluminum double hydroxide and nickel-aluminum double hydroxide, and is optionally lithium-aluminum double hydroxide.

11. The production method according to claim 10, wherein The preparation method of the lithium aluminum double metal hydroxide comprises the following steps: mixing metal Al and a solution containing Li + and OH - , performing a hydrothermal reaction, and obtaining the lithium aluminum double metal hydroxide.

12. The method of making according to claim 11, wherein, The particle size D50 of the metal Al is 0.1-0.3 μm. Optionally, the Li-containing solution + and OH - The solution containing Li and OH includes a LiOH solution with a concentration of 1-5 mol / L. Optionally, the molar ratio of Al element in the metal Al to Li element in the solution containing Li + and OH - is 0.1 to 2. Optionally, the temperature of the hydrothermal reaction is 50-70 ℃, and the time of the hydrothermal reaction is 20-24 h.

13. The method of making according to any one of claims 9-12, wherein, The mass fraction of the layered double hydroxide is 4-6% based on 100% of the mass of the slurry. Optionally, the solid content of the dispersion liquid containing polymer microspheres is 28-32%. Optionally, the mass fraction of the polymer microspheres is 4-6% based on 100% of the mass of the slurry. Optionally, the binder and the dispersant are further added in the mixing process of step (1). Optionally, the mass fraction of the binder is 5-7% based on 100% of the mass of the slurry; Optionally, the mass fraction of the dispersant is 0.1-0.5% based on 100% of the mass of the slurry; Optionally, the solid content of the slurry is 13-19%.

14. The method of making according to any one of claims 9-13, wherein, The preparation method specifically comprises the following steps: (I) adding metal Al with a particle size D50 of 0.1-0.3 μm into a solution containing Li + and OH - , then subjecting to hydrothermal reaction at 50-70 °C for 20-24 h, after solid-liquid separation and washing, drying at 60-70 °C for 5-8 h to obtain lithium-aluminum bimetallic hydroxide; The solution containing Li + and OH - is a LiOH solution, the concentration of the LiOH solution is 1-5 mol / L; the molar ratio of Al element in the metal Al to Li element in the LiOH solution is 0.1-2; the lithium aluminum double metal hydroxide has a layered porous structure, a specific surface area of 25-40 m 2 / g, an average pore size of 3.0-4.5 nm, and a particle size D50 of 0.2-0.4 μm. (II) mixing the lithium aluminum bimetallic hydroxide, the dispersion liquid containing polymer microspheres and the solvent at a rotation speed of 1800-2000 rpm for 2-3 h, then adding a binder to the obtained mixing product, mixing at a rotation speed of 1000-1200 rpm for 1-2 h, and then adding a dispersant, mixing at a rotation speed of 500-800 rpm for 0.5-2 h to obtain a slurry; The polymer microspheres comprise polyethylene wax microspheres, the polyethylene wax microspheres have a core-shell structure, the material of the inner core comprises hydroxyl polyethylene, and the material of the outer shell comprises polyacrylate; the particle size D50 of the polyethylene wax microspheres is 0.8-1.2 μm; the solid content of the dispersion liquid containing polymer microspheres is 28-32%; the mass ratio of the polymer microspheres to the lithium aluminum bimetallic hydroxide is (1-1.5):1; the binder comprises any one or a combination of at least two of acrylic acid, polyacrylate or polyurethane; the dispersant comprises an anionic surfactant and / or a polymer dispersant; and the solid content of the slurry is 13-19%; (III) coating the slurry on at least one side surface of a base film by using a micro-concave roller coating method, and drying at 60-70 ℃ to obtain the separator.

15. A battery, wherein, The battery comprises the separator of any one of claims 1-8 or the separator prepared by the preparation method of any one of claims 9-14. The battery comprises the separator of any one of claims 1-8 or the separator prepared by the preparation method of any one of claims 9-14.

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